This application incorporates by reference Taiwanese application Serial No. 89118278, Filed Sep. 6th, 2000.
1. Field of the Invention
A invention relates in general to a dual-sided chip package, and more particularly to a dual-sided chip package without a die pad.
2. Description of the Related Art
A leadframe is commonly used for providing a die pad capable of mounting dies in the packaging process of an Integrated Circuit (IC) die. The leadframe includes a set of lead fingers for providing the electrical connection between the IC die and external circuitry. A method for constructing a dual-sided chip package is disclosed in U.S. Pat. No. 5,527,740.
Referring to FIG. 1, a cross sectional view of the traditional dual-sided chip package is shown. In the chip package 100, the dies 102 and 104 are respectively mounted on the die pad 109 by using the adhesives 106 and 108. The bonding wires 110 and 112 couple the die 102 with the inner lead fingers 114 and 116 while the bonding wires 118 and 120 couple the die 104 with the inner lead fingers 114 and 116. The inside of plastic mold 122 includes the die pad 109, the dies 102 and 104, the bonding wires 110,112, 118 and 120, and the inner lead fingers 114 and 116.
While applying the traditional dual-sided chip package to the Thin Small Outline Package (TSOP), however, the flow of plastic between the surface 124 and the die surface 126 during plastic injection molding is slowed due to the short distance L between the surface 124 and the die surface 126. This might cause a backflow effect and generate voids.
The dies 102 and 104 have to be ground to 6 mil (=0.15 mm) conventionally. However, it might raise the manufacture cost to grind the dies 102 and 104. Besides, it is hard to handle the ground dies and the defect rate gets higher.
In addition, the Coefficient of Thermal Expansion (CTE) of the dies 102 and 104 and the die pad 109 are different. In FIG. 1, since the dies 102 and 104 are respectively mounted on the die pad 109 by using the adhesives 106 and 108, the variation of the temperature caused in the packaging process generates thermal stress due to the different speed of thermal expansion or shrinkage. The dies 102 and 104 may shell off or break as a result of the thermal stress effect. The thinner the dies 102 and 104, the more serious the shelling and breaking.
Furthermore, the die pad 109 of the traditional dual-sided chip package is supported by two or four support bars in the packaging process. Therefore, the different flows of plastic in the up, down, right and left directions might cause vibration and floating of the die pad 109 and the dies 102 and 104 during the plastic injection molding and then the bonding wire 110, 112, 118 and 120 might be exposed outside. Thus, special control is needed for preventing the exposure of the bonding wire and high deficiency.
It is therefore an object of the invention to provide a dual-sided chip package without a die pad. Without using the die pad, the distance between the die surface and the plastic surface gets longer. Thus, it enables a large decrease in the probability of generating voids with no need to grind the dies according to this invention. Besides, it improves the vibration and floating of the die pad in the manufacturing process and thus prevents the exposure of the bonding wire and the shelling off or breaking of the dies.
The invention achieves the above-identified objects by providing a dual-sided chip package without a die pad including a leadframe, first die, first bonding wire, second bonding wire, second die, third bonding wire, fourth bonding wire and plastic mold. The leadframe includes a first inner lead finger and a second inner lead finger. The first side of the first die is attached to the first inner lead finger and the second inner lead finger. The first bonding wire and a second bonding wire couple the first die with the first inner lead finger and the second inner lead finger respectively. Besides, the second die attached to the first side of the first die, wherein the second die is disposed between the first inner lead finger and the second inner lead finger. The third bonding wire and the fourth bonding wire couple the second die with the first inner lead finger and the second inner lead finger. The inside of the package includes the first die, second die, first bonding wire, second bonding wire, third bonding wire, fourth bonding wire, first inner lead finger, and second inner lead finger.
The invention achieves the above-identified objects by providing another dual-sided chip package without a die pad including a leadframe, first die, first bonding wire, second bonding wire, second die, third bonding wire, fourth bonding wire and plastic mold. The leadframe includes a first support bar, a second support bar, a first inner lead finger and a second inner lead finger. The first support bar and the second support bar are disposed between the first inner lead finger and the second inner lead finger. The first side of the first die is attached to the first support bar and the second support bar and the first die is disposed between the first inner lead finger and the second inner lead finger. The first bonding wire and a second bonding wire couple the first die with the first inner lead finger and the second inner lead finger respectively. Besides, the second die attached to the first side of the first die, wherein the second die is disposed between the first support bar and the second support bar. The third bonding wire and the fourth bonding wire couple the second die with the first inner lead finger and the second inner lead finger. The inside of plastic mold includes the first die, second die, first bonding wire, second bonding wire, third bonding wire, fourth bonding wire, first support bar, second support bar, first inner lead finger, and second inner lead finger.
The invention achieves the above-identified objects by providing the other dual-sided chip package without a die pad including a leadframe, first die, first bonding wire, second bonding wire, second die, third bonding wire, fourth bonding wire and plastic mold. The leadframe includes a first bus bar, a second bus bar, a first inner lead finger and a second inner lead finger. The first bus bar and the second bus bar are disposed between the first inner lead finger and the second inner lead finger. The first side of the first die is attached to the first bus bar and the second bus bar and the first die is disposed between the first inner lead finger and the second inner lead finger. The first bonding wire and a second bonding wire couple the first die with the first inner lead finger and the second inner lead finger respectively. Besides, the second die attached to the first side of the first die, wherein the second die is disposed between the first bus bar and the second bus bar. The third bonding wire and the fourth bonding wire couple the second die with the first inner lead finger and the second inner lead finger. The inside of plastic mold includes the first die, second die, first bonding wire, second bonding wire, third bonding wire, fourth bonding wire, first bus bar, second bus bar, first inner lead finger, and second inner lead finger.